Development of Highly Sensitive Ion Imager Corresponding to Real-Time Readout Having Single-Ion Detectability

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We designed a new type of stacked complementary metal--oxide--semiconductor active pixel sensor (SCAPS) for charged particles with real-time readout and single-ion detection capabilities. Here we present the characteristics of a new imager, SCAPS-II, which implements a newly devised pixel structure of 504\times 504 pixels for high sensitivity and a noise-reduction mechanism with analog accumulation capabilities inside the column readout circuits. The sensitivity for ions was estimated to be 150 μV/ion under 10 keV Si+ ion irradiation, which is 5 times greater than that of conventional SCAPS. The noise floor was at the 3 ion level without the noise-reduction mechanism at a frame rate of 0.16 s/frame. The noise reduction mechanism reduced the noise to the 1.7 ion level at 0.3 s/frame with 13 samplings. A combination of the noise-reduction mechanism and a multiple-frame-averaging technique achieved a noise level of 0.3 ions. Single-ion detectability was demonstrated using a combination of the noise-reduction mechanism and the multiple-frame-averaging technique that reduced the noise to the 0.3 ion level with 13 samplings, employing an integration circuit and 50-frame averaging at 14.4 s/frame.
2012-07-25